This invention relates to experimental apparatus and method for measuring gyroscopic stability of gun launched spinning projectiles. The present invention permits simulation of a spinning projectile in free-flight conditions for the purpose of providing real-time motion rate results without extensive data manipulation.
In the past, spin stability measurements were frequently made in fixtures employing the forced-mode principle. In this technique a fixture, having provision for holding and spinning a projectile and forcing a simultaneous coning motion, is used to determine the projectile's stability characteristics by computational means. In this procedure the projectile is permitted to despin freely while being held at a constant coning angle. The problem with this method is that inconsistancies in the friction of the supporting ball bearing races have led to questionable test results.
In the prior art devices which utilize spherical air bearings to test a spinning projectile model in a supersonic wind tunnel, it has been necessary to locate the support bearing inside the model and with a rear oriented strut to support the bearing and to minimize aerodynamic flow interference. The problem with the aforementioned apparatus is that the strut support severely limits excursions for most realistic model configurations.